1. Field of the Invention
The invention relates to a leak detection device for the pressure vessel of a gas cooled nuclear reactor. Typically, reactors of this type utilize a single or double wall liner in cavities of a concrete pressure vessel. More particularly, the invention concerns an arrangement of detection spaces surrounding at least weak locations of the liner and conduits on the concrete side of the liner to receive the cooling gas escaping upon the occurrence of leakages. The detection spaces are connected for the conduction of the cooling gas with at least one gas collector equipped with an indicator by means of connecting lines.
2. Background of the Prior Art
Pressure vessels of concrete or reinforced concrete for nuclear reactors must be provided in most cases with a metal inner liner for the sealing of the vessel walls. Requirements concerning the properties of the material of the liner are very high. This is particularly true for liners of high temperature nuclear reactors, cooled by means of gas. In spite of the strict construction specifications, which also require proof of the durability of the pressure vessel in the event of a series of hypothetical failures, the possibility that in time leakages may occur, cannot be completely excluded.
To contain leakages of this type occurring in the area of the liner and the cooling gas lines one leak detection device is also known. This device comprises a tubing system arranged for the detection of leaks on the side of the concrete in the vicinity of the liner. Individual pipes are installed in the form of a quadratic area grid. Each pipe has at its connection point with another pipe a fitting extending directly to the rear side of the liner. This is achieved by providing each pipe at its free end with a sliding sleeve of a porous material. The porous material is pressed against the liner prior to cementing. This snuffing nozzle provides direct contact of the orifice cross-section of the pipe with the liner. The detection installation may be further expanded so that certain areas of the liner that appear to be especially susceptible to leakage can be given individual attention. Such locations are represented particularly by welds and the passages of fittings. To detect potential leakages in the area of the welded joints for example, a hollow detection space is formed on the side of the concrete. This detection space is formed by welding sheet metal to the liner. The detection cavity formed in this manner is connected by means of tubing with the above-mentioned leak detection system.
A disadvantage of this known leak detection installation is its cost. The particularly high costs result from the fact that the detection cavities are arranged around the welded joints. They must be prepared individually to adapt them to the existing external contours of the structural elements of the reactor. Subsequently, these shapes must be welded to the liner by skilled welders, which further adds to the cost.
A further leakage installation for a double walled liner is also known. This installation has a system of channels. The system is arranged between the insulating concrete placed between the two walls of the liner and serves as a means to dry out the concrete and provide thermal stabilization of the insulating concrete during the construction phase. During the operation of the reactor, the channels are utilized for leak detection. The channels are prepared by placing thin tubing, hose members or round shapes into the concrete during its batch pouring and subsequently pulling them out. With the combination of the double walled liner surrounding the insulating concrete and the enclosed channel system, all leakage can be safely drained off so that the eventual cracks that form in the reinforced concrete do not lead to a buildup of pressure. The preparation of the leakage channels in the insulating concrete is a disadvantage in itself. Particularly in locations where there are deviations from the straing line, vertical arrangement significant problems may be expected. In case of a multiple cavity design, the detection network with vertical and horizontal channels will result in a comparatively complex geometry.
Still another leak detection arrangement is known from West German Offenlegungsschrift No. 23 27 394 for a pressure vessel with a single wall liner. The arrangement comprises channels on the concrete side in the vicinity of the liner, closed at least at one of their ends. There are surrounded by capillaries opening into the channels. The open ends of the channels are combined into a group of channels connected with a pump. The installation of the capillaries formed by finely porous tubular lines, particularly in areas characterized by a complex geometry is disadvantageous.